Vehicular headlamps with a leveling device are known for performing leveling adjustment to adjust an optical axis direction that changes due to the weight of objects loaded in a vehicle and a loading position (see, e.g., U.S. Pat. Nos. 6,428,196, 6,918,687).
The leveling device has respective predetermined portions disposed or supported in a case body, and includes: an adjusting screw that is connected to a tilt member such as a reflector whose illuminating angle of radiated light is changed by tilt movement; a shaft that supports the adjusting screw so as to be rotatable in a shafting direction and immobilized in an axial direction; a worm wheel that is rotatably supported by the case body and immobilized in the axial direction, as well as screwed to the shaft; and a motor that acts as a source of driving force to rotate the worm wheel.
In the foregoing leveling device, leveling adjustment is performed as follows. Driving force from the remote-controlled motor rotates the worm wheel, which sends the shaft screwed to the worm wheel in the axial direction. The adjusting screw supported by the shaft is fixed to the shaft and thus moved in the axial direction, tilting a tilt member such as the reflector, and changing the illuminating angle of radiated light.
In the foregoing leveling device, the shaft and the adjusting screw supported thereby are fixed together and moved in the axial direction to perform leveling adjustment. Therefore, means are used for restricting the movement of the adjusting screw in the axial direction with respect to the shaft.
An engagement projection portion is provided to restrict the movement of the adjusting screw with respect to the shaft. The engagement projection portion inwardly projects toward an end portion in the axial direction of the shaft, and an outwardly extending flange portion is on the adjusting screw which forms an engagement groove that engages with the engagement projection portion or a stepped portion for engagement. The engagement projection portion of the shaft and the engagement groove, or stepped portion for engagement, of the adjusting screw are engaged, and an opening edge on another end side of the shaft and the flange portion of the adjusting screw are engaged. Accordingly, movement in the axial direction of the adjusting screw with respect to the shaft is restricted.
According to the leveling device, engagement of the shaft and the adjusting screw is achieved by inserting the adjusting screw from the axial direction. In general, the shaft is formed from a resin material and configured such that a portion having the engagement projection portion elastically deforms.
In other words, as shown in FIG. 5, a portion of a shaft a having an engagement projection portion b is elastically deformed so as to deflect outward as a result of insertion of an adjusting screw c (a state indicated by dashed lines in FIG. 5). By positioning the engagement projection portion b corresponding to an engagement groove d of the adjusting screw c, the elastically deformed portion of the shaft a flexes back to normal such that the engagement projection portion b and the engagement groove d are engaged (a state indicated by solid lines in FIG. 5).
Dimensions of the engagement projection portion b and the engagement groove d are set taking into account a trajectory and tolerance of the engagement projection portion b when being inserted into the engagement groove d. In a state where the engagement projection portion b and the engagement groove d are engaged, a slight clearance D is created therebetween in the axial direction of the adjusting screw c. The clearance D is set within a range of 0.05 mm to 0.17 mm, for example.
Accordingly, the application of force in the axial direction to the adjusting screw c by external vibrations or the like may move the adjusting screw c with respect to the shaft a in the range of the clearance D, if the shaft a has little holding power with respect to the adjusting screw c. Consequently, a problem occurs in which the angle of a tilt member such as the reflector changes a corresponding amount, which then changes the illuminating angle of radiated light.
In addition, depending on the material of the shaft a and the adjusting screw c, as FIGS. 6 and 7 show, the adjusting screw c may expand greater than the shaft a at high temperatures. Consequently, a stepped portion of the engagement groove d may deform, pushing into the engagement projection portion b (see FIG. 6), and forming an indentation e on the engagement projection portion b (see FIG. 7) when the temperature returns to normal, thereby enlarging the clearance D.
If the clearance D is enlarged in such a manner, the amount of movement of the adjusting screw c with respect to the shaft a increases when force is applied in the axial direction to the adjusting screw c by external vibrations or the like. Accordingly, the change amount for the illuminating angle of radiated light also increases.
Hence, it is an object of a leveling device for a vehicular headlamp according to the present disclosure to resolve the foregoing problems and prevent misalignment of an adjusting screw in the axial direction with respect to a shaft.